Gas heating appliance



Aug. 6, 1935. G. HEGWEIN El AL 3 GAS HEATING APPLIANCE Filed Feb. 13, 1933 2 Sheets-Sheet 1 fly! 199.2

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GAS HEATING APPLIANCE Filed Feb. 1;, 1953 2 Sheets-Sheet 2 Aug. 6, 1935.

Patented Aug. 6, '1935 PATENT OFFICE Gas HEATING APPLIANCE Georg Hegwein, Friedrich Wilhelm Stockmeyer, and Curt Steinhardt, Stuttgart, Germany,,as-

signors to Junkers & 00. G. m.

Germany b. IL, Dcssau,

Application February 13, 1933, Serial No. 656,612

In Germany February 17, 1932 7 Claims.

; draught operate safety devices, which effect the closing of the main gas valve, arranged in advance of the burner. It has already been proposed to provide a back-draught safety device in which the returning waste gases due to a backdraught are conducted to a guardian flame,

which controls the main gas valve-for example, by thermostatic meansby the main valve being held open by the burning guardian flame, whilst it automatically closes on the extinction of the guardian flame. If a back-draught occurs, the guardian flame becomes extinguished owing to the deficiency in oxygen of the waste gases supplied to it, so that the main valve automatically closes. By this means the main burner is also extinguished and the production of further uantitles of waste gases is prevented.

. In this proposal however, both the waete gases ascending from the main burner and the waste gases returning from the outlet pipe are conducted to the guardian flame. This arrangement has the drawback that in a back-draught caused by strong wind too much fresh air from the chimney might be contained in the waste gases flowing back from the outlet pipe, so that the guardian flame was not extinguished quickly enough.

; only from the current of waste gases coming from the main burner, and in fact at a place where the gases from the burner have a strong upward movement, and where on the damming back or return flow an excess pressure occurs, thus, for instance, a little above theair damper openings of the draught hood or outlet conduit. By this 'arrangement it is possible to take a partial current from the burner waste gases poor in oxygen, which fully suflices to extinguish the guardian flame very quickly and with certainty. The effect of this arrangement can be considerably improved if the pipe is cooled in which the current 'of extinguishing gas taken from the current of burner waste gases is conveyed. In the cold pipe the extinguishing gases are rapidly cooled and descend by their own weight in the pipe to the guardian flame to be extinguished. Consequently, only a quite small force is necessary to introduce the waste gases into the pipe, because the descending cold extinguishing gases exert a suction action 'on the upper end of the descending pipe which facilitates the entrance of the waste gases. The arrangement, in fact, comes into operation so easily that it is necessary in certain circumstances to provide retarding means to prevent a too frequent extinction of the guardian flame, for instance, during short gusts of wind. The employment of a branched extinguishing gas pipe makes it particularly simple to make the action of the extinguishing gases on the guardian flame dependent in a quite definite manner on the duration and strength of the back-draught. In order to delay the action of the back-draught on the guardian flame, it suffices to provide one or more enlargements in the extinguishing gas pipe leading from the outlet pipe to the guardian flame, so that the waste gases forced during a back-draught into the extinguishing gas pipe must first fill these enlargements before they can reach the guardian flame. By making the enlargement of a suitable size the duration or strength of the back-draught can be exactly determined at which an extinction of the guardian flame, and thus a shutting off of the main burner, shall occur. If, on the other hand, it is desired to increase the speed of response of the protective device, a guide surface may be arranged above the inlet opening of the extinguishing gas pipe by which the waste gases returning from the outlet pipe which are strongly mixed with air and thus are rich in oxygen are led off, and are, for'instance, conducted away through the draught hood, whilst the waste gases which are poor in oxygen coming from the main burner are held back, as under a roof, so that they pass more easily into the extinguishing gas pipe.

Several examples of construction of the invention are shown in the drawings, in which- Figures 1 and'2 are diagrams of a liquid heater having a guardian flame safety device, showing normal draught and in the case of a back draught, respectively.

Figure 3 shows the same arrangement with a guide plate inserted.

Figure 4 is a diagram of a gas heating stove having a. pilot flame safety device.

Figure 5 is a vertical section through a bath-v room geyser having 'a retarded back-draught safety device, but with certain interior parts shown in side elevation.

Figure 6 is a rear elevation of the geyser shown in Figure 5, with the back wall removed.

Figure 7 is a partial sectional view on an enlarged scale of a modified form of tlr guardian flame burner shown in Fig. 5 and showing in side openings at the bottom of the hood. It is to -be understood, of course, that the outlet pipe I3 is connected to the flue or chimney of the building or room in which the heater is located, and under normal draft conditions there will be an up draft through the combustion chamber H, the draft hood l2, the outlet [3, and the flue or chimney of the building. Under this normal draft condition, air enters through the bottom opening l5 of the hood and so dampens the up'draft through the combustion chamber as to prevent excessive amounts of cold air being drawn through that chamber which would unduly cool its walls and thereby diminish the heating eifect of the main gas burner. A main gas pipe l8 leads above a main gas valve 23 to the main burner IS. The diaphragm 24 of this main gas valve has a throttle opening 25 through which a weak current of control-gas flows constantly from the high pressure side 26 into the controlling chamber 21. From the controlling chamber 21 a gas pipe 28 leads to the burner 29 of a guardian flame, which acts on a thermostatic valve 32 controlling the control-gas pipe 28.

In the example of construction shown, the guardian flame burner 29 is formed as a' safety pilot burner, and in fact by the burner casing 23 being closed by a thermostat disc 3|], which contains a burner opening 3| and carries a valve plate 32. If the thermostat disc 30 is cold, it presses the valve plate 32 on its seat and thereby closes the outlet of the control-gas pipe 28, so that the control-"gas collects in the control chamber 21 of the main valve and presses the diaphragm 24 against the main valve seat (Figure 3). If, however, the hermostat disc 30 is heated by a flame, for example, the guardian flame, it curves or bends upwardly and opens the valve 32, so that the pressure escapes from the control chamber 2'! and the main gas valve opens. This guardian flame, whose burner may, of course, be of a difierent construction, is so arranged that it lies in the path of the extinguishing gasesand is extinguished by them.

In front of the outlet pipe l3 a pipe connection 43 branches ofl and extends downwardly outside the waste gas conduit of the heat-exchanging device into immediate proximity to the guardian flame. 'While not essentiaLrit may be advantageous to cover this pipe with heat insulating material as a protection against absorption by the descending gases of heat through the metal wall of the pipe from-the room outside.

With normal draught, the waste gases take their.

way from the burner chamber H through the draught hood [2 and the outlet pipe l3 into the chimney (Fig. 1). When a back-draught occurs (Fig. 2) the waste gases ascending from the burner l6 into the outlet pipe l3 encounter acolumn of waste gas and air which conflicts with their ascent. Consequently, an excess pressure occurs in the draught hood l2, which tends to 7 force the waste gases through its bottom openings which are deficient in oxygen (Fig. 2). After the extinction of the pilot flame the thermostat disc 30 becomes cold, and at once presses the valve plate 32 on its seat, whereby the control-gas pipe ciently great to force the waste gases into the extinguishing gas pipe 43.

In the liquid heater shown in Figure 3 a guide plate 45 directed obliquely downwards is arranged above the inlet opening of the extinguishing gas pipe 43. The guide plate 45 catches the waste gases poor in oxygen rising from the burner l6 and holds them back in front of the extinguishing gas pipe 43. The waste gases returning from the chimney. and mixed with-air are prevented,

on the other hand, by the plate 45 from entering into the pipe 43 and are conducted to the bottom opening of the hood.

the gas heating stove shown in Figure 4, the main gas pipe I8 is closed by a thermostat valve 46 when the stove is out of use. If the diaphragm of the valve is heated by a pilot flame directed against it, the valve 46 opens the gas passage and gasflows to the main burner IS. The burnt gas rises upwards in the heating bodies 11 and escapes through the outlet pipe 48. From the outlet pipe 48 an extinguishing gas pipe 43, as before, leads to the pilot burner 29. On a back-draught, the pent up waste gases pass into the pipe 43 and flow in it to the pilot flame, which is put out and thereby effects the closing of the thermostatic main gas valve 46. In the extinguishing gaspipe 43 a box-shaped enlargement 49 is provided, in which the downwardlyflowing extingiushing gases first collect before they reach the pilot flame. The pilot flame is thus prevented from becoming immediately extinguished at every brief back-draft, for example, during short gusts of wind. 7

It is further to be noted that in the Fig. 4 construction the discharge-end portion of the pipe 63 is formed .asa mouth-piece fitting over the pilot burner 29 so that when a sufl'icient backdraft pressure occurs in the discharge flue'48 to cause a flow of waste gases from that flue through the pipe 43 and its enlargement 49, the outlet mouth-piece of the pipe 43 discharges those gases directly over the outlet orifice or jet of the pilot burner. end of pipe 43' of the Fig. 4 construction'is the The outlet mouth-piece on the discharge same as the outlet mouth-piece on the discharge end of the waste-gas pipe shown in Fig. 7 later to be referred to. v t

The geyser shown in Figure 5 has the usual construction of a through-flow heater'to be suspended on the wall. device and I2 the draught hood, which are both enclosed by a sheet metal outer casing 50, provided with the air-damper openings I5. the outlet pipe for the waste gases. The cold water passes through pipe 5 l through a valve 52 into a tubular worm 53 and is there heated by the ascending hot gases. The gas flows from the main gas'pipe l8 through a main gas valve 23 to the main burner IS. The pilot flame is here also used as the back-draught safety device.. The extinguishing gas pipe '43 in this case again His I0 is the heat-exchanging iranches from the draught hood l2, which pipe LS a descending pipe 44 leads inside the sheet netal outer casing 50 to the automatic safety )llot burner 29. s interposed in the descending pipe 44, and is ;urrounded by the casing 50. 'When a backiraught occurs in the outlet pipe for the waste gases, a rise in pressure occurs in the draught aood 12' due to the hot burner gases. Conseuently, a part of the waste gases poor in oxygen forced into the extinguishing gas pipe 43 and :onducted downwards by the descending pipe 64. in order to strengthen the downward flow of he extinguishing gases in the descending pipe 44, :he descending pipe and the enlargement 49 are separated by a partition wall 58 from the adjacent .nterior portion of the casing 50 containing the neat-exchanger H). The partition wall 58 is to seep off the heat from the extinguishing gas pipe 13, and the receptacle 49 interposed therein.

A special cooling arrangementiwater or air) I may also be provided for the extinguishing gas pipe 43, 44 and the receptacle 49' interposed therein. The waste gases quickly cooling in the cold pipe and receptacle rapidly descend therein and thereby exert a suction action on the waste gases flowing back from the draught-interrupting hood I2. When the extinguishing gases have extinguished the pilot flame, the diaphragm of the pilot burner 29 closes the pilot valve 32, and pressure occurs in the control chamber 21 of the diaphragm valve 23 which presses the diaphragm against the gas outlet and closes it.

Figure 7 shows on a larger scale a modified form of the safety pilot burner 29 of the Figs. 5 and 6 construction having a releasable connection with the waste gas pipe 43, 44 and an additional gas supply pipe for initial ignition purposes. Fig. '7 also shows a mouth-piece on the dischargeend portion of the waste-gas pipe the same as the mouth-piece employed on the discharge-end portion of the waste-gas pipe 43 in the Figs. 4, 5, and 6 constructions. The valve casing 29' is secured to the additional gas-supply pipe 59 of the pilot burner, and is closed by a diaphragm 30 provided with a burner opening3l 32 is a valve member, which, when the pilot flame is out, is

pressed by the diaphragm 30 by the intermediary of a spring 6| on "the valve seat 60. The controlling gas reaches the valve by a pipe 28 as in the Fig. 5 construction. When the diaphragm f -l is heated by a flame, it curves upwardly, raises the valve 32 from the seat 60, and allows the controlling gas to flow out. 63 is an opening through which a current of ignition gas can be sent through the pipe 59 to the burner opening 3| by by-passing the closed valve 32, in order to form an ignition flame. A flexible metal pipe 64 is provided for releasable connection with the end of the extinguishing gas pipe #3, 44 shown in Fig. 5, and this flexible pipe 64 terminates in a mouth-piece 65. This mouth piece 65 is formed like a lid or cover which extends over the valve casing 29' of the pilot valve and closes it with the exception of an opening 61 opposite the burner opening 3| in the cover-plate 66 of the mouth-piece. A space is left between the coverplate 66 and the diaphragm 30 through which the extinguishing gases can flow from all sides to the burner opening 3| and escape through the opening 61. In this way the pilot flame passing through the cover opening 61 is extinguished with quickness and certainty without affecting the flames of the main burner, which continue to burn undisturbed until the main gasvalve 23 A flat box-shaped receptacle 49 (shown'in Fig. 5) is closed owing to the extinction of the pilot flame in the manner already several times described.

The thermostatic disc employed in all the examples of construction of the invention may be either a bimetallic or a single metal disc, as desired, but preferably, and as shown for the thermosstatic disc 30 in Figs. 1 to 3, inclusive Figs. 5 and "I, and for the thermostatic disc 46 in Fig. 4, this element is a single metallic sheet.

While the part of the apparatus indicated at i 2 in Figs. 1, 2, and 3, and i2 in Figs. 5 and 6, specifically functions as a draught hood, and has been termed a draught hood in the foregoing part of the specification, and the part 13 has hereinbefore been referred to as an outlet pipe .from that hood, that hood and pipe also conthe pilot flame, and means opening into said flue and terminating adjacent said pilot burner and operating to extinguish the pilot flame upon an increase in gas pressure in said flue due to a back draught therein.

2. A safety gas appliance comprising a casing having a main gas burner, a flue leading from said casing, a pilot burner positioned to ignite said main burner, gas-supply conduits leading to said burners, a cut-off valve in the main-burnersupply conduit, means including means responsive to the heat of the pilot burner operative to maintain said cut-off valve open when the pilot flame is on and to close the same upon extinguishment of the pilot flame, and conduit means opening into said flue and. terminating adjacent the jet of said pilot burner and operating to discharge a flame-extinguishing stream of waste gas against said jet upon an increase in gas pressure in said flue due to a back draught therein, said conduit means comprising means operating to retard the speed of flow of the waste gases therethrough. be low the speed of backflow of gases in said flue.

3. A safety gas appliance comprising a casing having a-main gas burner, a flue leading from said casing, a pilot burner positioned to ignite said main burner, gas-supply conduits leading to said burners, a cut-off valve in the main-burner-supply conduit, means including means responsive to the heat of the pilot burner operative to maintain said cut-off valve open ,when the pilot flame is on and to close the same upon extinguishment of the pilot flame, and conduit means opening into said flue and terminating adjacent the jet of said pilot burner and operating to discharge a flame-extinguishing stream of waste gas against said jet upon an increase in gas pressure in said flue due to aback draught therein, said conduit means comprising a pipe having a portion intermediate its length of enlarged diameter and a contracted terminal or discharge-end portion.

4. A safety gas appliance comprising a casing having a main gas burner, a flue leading from said casing, said flue comprising a draught hood for said casing having walls upwardly converging to a restricted outlet aperture for said hood, a pilot burner positioned to ignite said main burner, gas-supply conduits leading to said burners, a cut-off valve in the main-burnerf'supply conduit, means including means responsive to the heat of the pilot burner operative to maintain said cut-oi? valve open when the pilot flame is on and to close the same upon extinguishment of the' pilotflamaand; conduit means opening into said hood in the region of minimum crossfrom said main gas. burner into said conduit means upon an, increase of gas pressure in said flue due to a back draught therein and to deflect down-flow back-draught gases-away. from said open connection or inlet end of said conduit means.

6. A safety gas appliance comprising a casing having amain gas burner, a flue leading from said casing, a pilot burner positioned to ignite said main burner, gas-supply conduits leading to said burners;;a cut-offvalve-in the main-burnersupply conduit, means including means responsive to the heat of-the pilot burner operative to maintain said cut-oft valve open when the pilot flame is on and to close thesarne upon extinguishment of the pilot flame, and conduit means opening into said flue and having asitsterminal portion a mouth-piece fitting over said pilot burner with said mouth-piecezprovided with an outlet opening for the waste gases andpilot; flame whereby said conduit means operateslto discharge a flameextinguishing stream of wast'e'gases against said jet upon ah increase in gaspressure in said flue due to a back-draught therein.

'7. A safety gas appliance as defined in claim 6 and further characterized by said mouth-piece having a rim detachably mounting said mouthpiece on said pilot burner over the pilot jet.

GEORG HEGWEIN. FRIEDRICH, WILHELM STOCKMEYER. CURT STEINHARDT. 

